The ecology of rafting in marine crustaceans
An extensive literature survey revealed that rafting on objects floating at the sea surface is a common dispersal mechanism in marine crustaceans. A great variety of objects including detached macroalgae, plastic items and wood have been found to serve as substrata for rafting organisms. A total of 365 crustacean species from all major taxonomic groups have been reported from floating objects. Amphipods (104 species) represent the most diverse group followed by brachyuran decapods (60 species). 296 species are facultative rafters. These animals usually have a benthic or pelagic life-style and inhabit floating items as a secondary habitat. However, 23 species, mainly represented by barnacles, have been identified as obligate rafters living exclusively on floating substrata. Most rafting crustaceans reproduce sexually, primarily featuring a gonochoric sexual system with few hermaphroditic species. Fertilization mode is internal in all species. Direct development of juveniles without pelagic larvae is the major developmental mode, facilitating the retention of juveniles close to the parental animals. Mobile species able to walk or crawl dominate on natural substrata that are exposed to biological degradation. Persistent substrata, however, are often colonized by sessile animals. Feeding mode of the animals also appears to depend on substratum characteristics. Many grazing species are found on floating macroalgae while suspension feeders and predators dominate on abiotic objects and wood. The high degree of functional and morphological diversity within the Crustacea allows these animals to colonize a great variety of floating substrata making rafting an efficient dispersal mechanism for this group.
Helmholtz Research Programs > MARCOPOLI (2004-2008) > CO2-Coastal diversity - key species and food webs